Mechanism of seepage failure of ground with air bubbles in multi-scale and proposal of counter-measure

根据代表性研究人员的数值分析，假定局部暴雨对河堤的破坏与堤防饱和有关，这是由于随着堤防渗流线的上升，从堤防表面渗出水和孔隙空气（气吹）吹出所致。由于处于城市化进程的下游的河堤是由以软质和细颗粒为主的沙质土壤构成的，因此认为河堤容易被封闭在河堤体内的孔隙空气破坏。在本研究中，通过使用配备降雨产生装置的堤防模型进行实验，研究了降雨渗透和河流水位上升所捕获的孔隙气团的行为。在采用透气性防水片防渗措施后，可以看出防雨渗和降低孔隙气压的效果。这种利用SPH的土-水耦合连续统分析方法的发展也成功地考虑了细颗粒流动的侵蚀过程。

Based upon numerical analysis developed by the representative researcher, the damage of a river dike caused by a localized torrential downpour is presumed to be related to the saturation of the dike, due to seepage water from the dike surface and blow off of pore air (air blow) following a rise in the seepage line in the dike. Since a river dike located at the downstream, where urbanization has been in progress, is composed of sandy soil consisting mainly of soft and fine particles, the river dike is considered to be easily damaged by pore air that has been enclosed within the dike body. In this study, by performing experiments using a dike model equipped with a rainfall generation apparatus, the behavior of a pore air mass captured by rainfall seepage and a rise in the river water level was investigated. When seepage prevention measures using a breathable-waterproof sheet had been taken, the effect of preventing rainfall seepage and that of reducing the pore air pressure were revealed. Development of this soil-water coupled continuum analysis using SPH was also succeeded with account for the process of erosion in which fine particles were flowed.